U.S. President Barack Obama says the new Iranian government's pursuit of a "more moderate course" should offer a basis for an agreement on Iran's nuclear program.
Addressing the opening session of the UN General Assembly on September 24, Obama told world leaders the roadblocks may be too big, but that the "diplomatic path should be tested" to resolve the Iran nuclear issue.
"America prefers to resolve our concerns over Iran's nuclear program peacefully, although we are determined to prevent Iran from developing a nuclear weapon," Obama said.
He said he had directed Secretary of State John Kerry to pursue diplomatic progress, in coordination with other world powers, to resolve the dispute over Iran's nuclear ambitions.
Iran insists its nuclear program is entirely peaceful.
Iranian President Hassan Rohani is due to address the forum later on September 24.
Despite earlier speculation that the two leaders might meet on the sidelines of the General Assembly, senior U.S. officials said it would not happen.
An Obama administration official, speaking on condition of anonimity, said the White House was open to a meeting between Obama and Rohani in New York, but the Iranians indicated it was too complicated.
Leaders of the two countries have not met face-to-face in more than 30 years.
Kerry will join representatives of the four other permanent UN Security Council members, plus Germany on September 26 in a meeting with Iran's foreign minister.
Syrian Response Too Weak
In his address, Obama also called on the UN Security Council to pass a strong resolution to ensure that the Syrian government keeps its commitments under a U.S.-Russia agreement to dismantle its chemical-weapon arsenal.
Obama told world leaders that the international community must enforce the ban on chemical weapons in Syria, and that the world's response to the Syria crisis had been too weak.
He said the evidence that Syrian President Bashar al-Assad's regime used chemical weapons in an August 21 attack near Damascus was "overwhelming."
"It is an insult to human reason -- and to the legitimacy of this institution -- to suggest that anyone other than the regime carried out this attack," Obama said.
He also called on Assad's allies to stop supporting his regime. "It's time for Russia and Iran to realize that insisting on Assad's rule will lead directly to the outcome that they fear: an increasingly violent space for extremists to operate," Obama said.
UN Secretary-General Ban Ki-Moon opened the 68th General Assembly at UN headquarters in New York earlier on September 24 with a call for a binding resolution to eliminate chemical weapons in Syria.
Ban also appealed to world powers to stop sending weapons to all sides in the Syria conflict.
The Syria conflict, which the UN says has killed more than 100,000 people, is expected to dominate speeches during the week of debates at UN headquarters in New York.
With reporting by Reuters, AFP, AP, and dpa